Vitamins C and E Against Alzheimer's?

Summarized by Robert W. Griffith, MD
March 12, 2004

Introduction

There have been a number of studies showing that some antioxidants, such as vitamin C and vitamin E, can reduce the risk of someone getting Alzheimer's. But they haven't been very conclusive - sometimes it's the vitamins contained in the diet that are important, or it's just one vitamin or the other that seems to work; and sometimes neither diet nor supplements have a protective effect.

There's good scientific reason to think that antioxidants should work in preventing the brain changes seen in Alzheimer's. So the publication of a new study of vitamins in the elderly is timely. Here's a summary of the findings reported in the Archives of Neurology.

What was done

Over 5000 elderly people living in Cache County, Utah, USA, were enrolled in the study; they were all over 65 (average age 75), and about 60% of them were women.

Extensive screening was done to detect any cases of dementia. In addition, each participant had an interview when they were quizzed about possible risk factors for dementia. It covered years of education, occupation, medical history, tobacco and alcohol use, and medications taken. Specific questions dealt with vitamin supplements. Participants were classified as vitamin E users (more than 400 IU daily), vitamin C users (at least 500 mg ascorbic acid daily), multivitamin users (so that they were taking vitamin E and/or C in lower daily doses), and vitamin B users (taking a formulation of B-complex vitamins).

Three years later, all the survivors (there were over 3200) were screened again for cases of dementia. Analyses were done to see if there was a decreased risk of getting Alzheimer's according to the use of the different vitamin supplements.

What was found

At the first screening, there were 355 people (7.5%) with dementia, and 200 of these had Alzheimer's. Three years later, there were 185 cases of dementia, of which 104 were Alzheimer's disease.

At baseline, roughly 17% of the participants reported taking vitamin C or E supplements (at the doses given above) for more than 2 years; these people were more likely to be female, younger, had more years of education, and were in better general health than the rest.

Analysis made at baseline (this is called a 'prevalence analysis'):

The use of vitamin E, vitamin C, and multivitamin supplements were all linked to a reduced risk of developing Alzheimer's disease. However, after making allowances for differences in age, gender, years of education, and general health, the linkage was only significant for the use of vitamin E and multivitamin supplements.

Looking at the combined use of vitamins, a very strong link was found between a lower risk of Alzheimer's and the use of vitamin C and vitamin E supplements together, whether taking multivitamins or not. Taking both vitamin C and E supplements would mean a 4- to 5-times lower risk of getting Alzheimer's.

Analysis three years later (called an 'incidence analysis'):

The results here were similar to those at baseline. The likelihood of Alzheimer's disease was slightly reduced with vitamin E and multivitamin supplements taken together, but much more markedly with the use of vitamin C and vitamin E supplements taken together. In this case, people were about 3 times less likely to develop Alzheimer's. Age and gender had no effect on these results.

Users of vitamin E or vitamin C supplements alone, or multivitamins alone, or B-complex vitamins, showed no differences in their likelihood of developing Alzheimer's disease.

Comment

This study suggests quite convincingly that antioxidant vitamins, in particular the combination of vitamin E and C supplements, may prevent Alzheimer's. However, the researchers point out that 'formal proof of such an effect can only come from randomized prevention trials'.

There does seem to be a possible scientific explanation for the better results with the two vitamins in combination. As vitamin C is water soluble and rapidly lost from the body, its role is limited to the reduction of the oxidized lipid-soluble vitamin E (i.e. 'recharging' the activity of vitamin E in the brain).

The present recommended daily allowance (RDA) for vitamin E is 22 IU (15 mg), while that for vitamin C (ascorbic acid) is 75-90 mg.¹ Multivitamin preparations usually contain these amounts, while individual vitamin supplements usually have up to 1000 IU of vitamin E and 500-1000 mg of vitamin C.

You're now probably wondering "Should I be taking 1000 IU of vitamin E and 500 mg of ascorbic acid (vitamin C) daily?" Up to now, we've usually suggested on these pages that eating a vitamin-rich diet is better than taking supplements. However, the results of this study are quite convincing. And the doses measured in the study (400 IU of vitamin E, 500 mg of ascorbic acid) are most unlikely to cause any health problems, while they obviously may do you some good. If still in doubt, ask your doctor.

Source

• Reduced risk of Alzheimer disease in users of antioxidant vitamin supplements. PP. Zandi, JC. Anthony, AS. Khachaturian,  et al., Arch Neurol, 2004, vol. 61, pp. 82--88

Footnotes
1. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium and Carotenoids.  Institute of Medicine, Washington, DC: National Academic Press, 2000

Related Links
Antioxidant Supplements: Can They Slow Mental Decline?
Fat Intake Appears to be Tied to Alzheimer's Risk
Wine Linked to Better Mental Function in Seniors
Diet to Prevent Alzheimer's?

Please take a moment to give us your comments. For questions about Health matters you may check our "Questions & Answers" Portal and Service.